Power driven ski

ABSTRACT

A power driven ski is divided by an aperture into anterior and posterior ski portions, which are held one to the other by a bridge so that their combined undersurfaces form a longitudinally smooth skiing undersurface throughout the length of the ski. A motor driven endless tread is circulateably supported around the posterior ski portion for thrusting against the snow over which the posterior ski portion slides.

BACKGROUND OF DISCLOSURE

This invention relates to skis, and specifically to a ski having powerdriven means for propelling a skier.

Presently there is a polarization between outdoor winter sportenthusiasts. The purists adhere to skis propelled by gravity, while themodernists enjoy the control of motor power together with the winteroutdoors environment by mounting a snowmobile.

A power driven ski, as explained in Richard F. Thompson U.S. Pat. Nos.3,645,348 and 3,710,881 (of which I am an assignee) which are hereinincorporated by a reference, provides the skier on the one hand withsome of the challenges of downhill skiing such as holding balance,steering and braking by body manipulation, etc., without being limitedto a "one-way" skiing on an often-crowded hill equipped with a ski lift.On the other hand, a power driven ski is much less cumbersome to use,transport and store than a snowmobile, less expensive to produce andmaintain, and provides a more exciting form of sport since it requiresthe skier's body participation and skill to a degree not experiencedwhile driving a snowmobile or other motorized vehicle.

Thus, a power driven ski opens to the skier the entire snow coveredoutdoors, and specifically the flat northern regions of the UnitedStates such as the Midwest region, to scout and enjoy in a new andexciting way.

SUMMARY OF DISCLOSURE

Briefly, a power driven ski is provided by combining an anterior skiportion with a traction unit comprising a posterior ski portion and apower driven endless tread circulateably supported thereon. It isimportant to combine the anterior ski portion with a traction unithaving certain features (which will be discussed herein shortly) so thatthe resulting power driven ski as a whole will achieve the object of thepresent invention which is:

To provide the skier with a unit that is worn on the foot and functionson the snow as a conventional ski, having a longitudinally smoothundersurface substantially throughout its length as a conventional ski,for enabling the experienced skier to execute the full range of skiingmaneuvers from straight line skiing, snow plowing and edging to christieand stem turns) while giving the skier, at the same time, the freedom toski on flat and hilly terrain (uphill or downhill) at a speed anddirection of his choice.

The features which are required of the traction unit, in addition to itsability to propell the skis and skier in order for the ski as a whole toachieve the above object, are as follows:

To have a longitudinally smooth snow contacting, stationary undersurfacethroughout its length,

To generate a minimal lateral reaction from the snow with the tread evenwhen sliding laterally,

To laterally support and shelter the tread so it is both functional andundisturbed by such lateral movement of the ski relative to the snow,(such lateral movement occurs extensively during turning and brakingmaneuvers),

to offer minimal resistance to powerless coasting or downhill skiing,and to be light and compact.

These and other features of the invention will be further discussed andillustrated with reference to the Figures in the following paragraphs.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a general side-view of a preferred embodiment of a powerdriven ski in its free position,

FIG. 2 is a sectional side-view of a posterior portion of the powerdriven ski shown in FIG. 1,

FIG. 3 is a sectional view of the power driven ski taken along the line3--3 marked on FIG. 2, with the tread removed.

FIG. 4 is a sectional view of the power driven ski taken along the line4--4 marked on FIG. 2,

FIG. 5 is a sectional view of the power driven ski taken along the line5--5 marked on FIG. 2, with the tread removed,

FIG. 6 is a sectional view of a modified embodiment of a power drivenski taken on a plane which is orientated relative to the modifiedembodiment as the plane of FIG. 4 is oriented relative to the preferredembodiment, and

FIG. 7 is a general side view of a power driven ski in use.

DETAILED DESCRIPTION OF THE FIGURES

A preferred embodiment of a power driven ski 10 (shown in FIGS. 1 to 5)comprises:

A ski 11 having an aperture 12 which divides it to anterior andposterior ski portions 13 and 14, respectively, which are held (andpositioned) one to the other by a bridge 15, so that the longitudinallysmooth anterior and posterior undersurfaces 16 and 17, respectively,unite to jointly form a longitudinally smooth snow contacting,stationary (relative to the ski, as in a conventional ski) skiingundersurface substantially (that is, neglecting the relatively small gapin the area of the aperture) throughout the length of the ski.

Conventional binding means which are located at the rear part of theanterior ski portion having, a front anchor 46, rear anchors 49 (oneshown), a lever 47 and a cable 48 are provided for attaching the ski 11to a skier's foot through a boot 45.

An endless tread 18 having at least one tension carrying member 19 inthe form of a roller chain containing attachment links to whichoutwardly protruding cleats 20 are attached for thrusting against snowpre-packed by the anterior undersurface 16 and on which the posteriorundersurface 17 slidingly bears and thereby maintains packed,circulateably supported around the posterior ski portion 14.

Means for circulateably supporting the tread 18 consisting of; a drivesprocket 26 coupled to a shaft 24 which is in turn being rotateablysupported by the bridge 15 through ball-bearings 50, which are affixedto the shaft with a snap ring 51, and an idler assembly 33 having asprocket 35 which is rotateably supported through a needle-bearing 37and a shaft 36 on a piston 34 which is slideably disposed in a bore atthe rearend of the posterior ski portion 14.

Motor means 21 which incorporate a centrifugal clutch and which isadapted to be carried by the skier on his back or hip area is coupled tothe tread 18 through a flexible shaft 22 and a right angle gear box 23for circulating the tread 18. Optionally the motor 21 can be mounteddirectly on the bridge 15 in which case a chain and sprockets drive mayreplace the flexible shaft 22 and the gear box 23.

A one-way clutch 25 formed in the hub of the sprocket 26 couples it tothe shaft 24 and permits the free circulation of the tread 18 duringpowerless coasting or downhill skiing. Further, the one-way clutch 25prevents the motor 21 from braking the tread and throwing the skier offbalance forwardly when the motor 21 suddenly slows down due to somemalfunction or due to a sudden release of the motor's throttle which isnormally controlled through an assembly comprising a trigger mechanism61 attached to one of the ski poles 62 which is connected to the motor21 through a flexible cable 60 by the skier's hand (note FIG. 7).

The engagement of the one cleat 20 with snow near the front of theposterior undersurface 17 is sequenced out of phase with thedisengagement of another one of the blades 20 near the rear of theposterior undersurface 17 to prevent the torque peaks that theengagement and disengagement imposes on the motor 21 through the shaft22 from accumulating at one point in time.

The tread 18 circulates from above to below the posterior ski portionthrough the aperture 12, over the front sprocket 26 which has a firstpitch-line radius, and thereafter over an arched ramp 43 having asubstantially larger pitch-line radius 44 (although not necessarily aconstant radius) for guiding the cleats in a downwardly direction on anarc into a gradual engagement with the snow. The reason for the archedramp feature can be best understood by looking at the process by whichthe cleat engages the snow.

The snow which is exposed to the cleat through the aperture has beenpre-packed by the passage of the anterior undersurface 17 over it, andoften, due to common weather processes, it is covered by an icy crust.As the tread 18 circulates over the sprocket 26, its various portionsassume a speed which is proportional to the radius along which theyswing. For example, if a tip 41 of the cleat 20 swings on a radius whichequals twice the pitch-line radius of the sprocket 26, its speed willdouble relative to the speed of the chain 19 (which is also the speedthat the cleats 20 and their tip 41 assume as they sweep along thestraight part of the posterior undersurface 17). In addition, as simplegeometrical considerations would indicate, if the cleat will becomeengaged with the snow while it is still passing over the sprocket 26,then its generous frontal area 42 will be forced into the snow ratherthan its sharp tip 41. Such a process of engaging the cleat 20 with thesnow by forcing its frontal area 42 into it while the cleat 20 movesmomentarily at an increased speed (i.e., reduced leverage) imposes atorque peak on the motor 21. This torque peak represents a power lossand gives start-ups from standing still an erratic "stick-slip"characteristic.

One remedy to correct the above mentioned problem would be tosubstantially increase the front sprocket's diameter, but this wouldhave several obvious drawbacks such as making the power driven ski muchmore cumbersome and heavy, especially in cases where the engine ismounted directly on the bridge 15 above the sprocket 26 (as one mayoptionally mount the engine). Further, a power driven ski with a largedrive sprocket would tend to translate flexing of the posterior skiportion 14 into a substantial change in the length of the chain 19 onone hand, and cause artificial flexing of the posterior ski portion 14on the other hand. Thus, substantial enlargement of the sprocket 26would negatively change the characteristics of the power driven ski.

In order to obtain the improvement that a large sprocket would offer tothe engagement process while avoiding its above discussed structuralpenalties, a combination of a small sprocket 26 followed by an archedramp 43 is employed. With this arrangement, the cleat 20 accomplishesthe majority of the turnover on the front sprocket, but as the cleat 20starts to effectively engage the snow it becomes guided along the archedcontour of the ramp 43 over which the cleats' turning process becomesslower. Thus, during the critical cleat 20-snow engagement stage, thecleat 20 moves as if it were turning over a larger sprocket than thesprocket 26 actually is (It should be noted that the arched ramp 43structure is used in this invention to smoothen out the engagementprocess of the protruding cleats 20, and not for obstacle negotiating.To negotiate obstacles, the power driven ski employs a curved portion atits very front section, as in regular skis and other tracked and glidingvehicles).

To further refine the graduality of the cleats' engagement with thesnow, their tip can be shaped to avoid a line contact with the snowsurface, but to replace it with a point or points contact by shaping thecleats' tip to form a line which is not parallel to the posteriorundersurface 17, as shown in FIG. 4, where the Cleat's tip 411 has aflat v shape and the next cleat behind it has a tip 412 with an invertedv shape.

It should be pointed out that during the disengagement process, similargeometrical considerations that were discussed above would make a largerear sprocket, or a combination of a second arched ramp ahead of therear sprocket 35, useful. However, disengaging from the snow is aprocess which offers less resistance than the engagement process duringwhich further packing of packed snow downwards occurs. Also, the chain19 carries maximum tension forces as it passes over the rear sprocket35, while it carries minimal tension forces when passing over the archedramp 43. Thus, the frictional forces between the rear arched ramp wouldbe several times higher than they are over the front arched ramp 43.Therefore, while its a designer's option to incorporate a rear archedramp, it is pointed out that the ratio between improvement inperformance to the structural and power loss penalties that a rear rampstructure represents is less favorable in the case of the rear archedramp versus a front one.

As explained in Thompson's U.S. Pat. No. 3,710,881 (which was previouslyincorporated by reference) it is important to effectively energize theposterior ski portion against the snow in order to prevent the snow frombeing blown away and to obtain forward thrust from the snow. For thispurpose, a dihedral angle of less than 180° between the anterior andposterior ski portions is called for by Thompson. In the presentinvention, as shown in FIG. 1, the posterior ski portion undersurface 17can be stepped (lowered) downwards relative to the anterior ski portionundersurface 16, forming a step which is indicated by numeral 55, toimprove the above mentioned energization of the undersurface 17 againstthe snow. This optional modification can be used together with, orwithout, Thompson's dihedral angle of less than 180°.

As the cleats 20 engage the snow they erect into it on their rear tipwhich is bent to form a sliding bearing 52 throughout the width of thecleat thereby causing the chain to assume a zig-zag configuration asviewed on a plane which is parallel to the chain 19 and perpendicular tothe posterior undersurface 17 (note FIG. 2). This zig-zag configurationcauses tension forces which are carried by the chain 19 to negatebending moments imposed on it by the cleats 20 through connecting links27 by offering the tension forces a lever arm 28 (which is slightlysmaller than the vertical distance between the axes of chain hinge pins29 and 30) to act on.

At the rear-end of the posterior ski portions, the idler assembly 33 isresiliently floating on a helical compression spring 38 and therebypermits the chain 19 to assume the above discussed zig-zag configurationwithout becoming stretched.

The chain 19 comprises a series of links (standard links 31, attachmentlinks 27, and a lock link 32) hinged one to the next by hinge pins 29and 30 which permit the pivoting of the chain as viewed on a plane whichis parallel to the chain 19 and perpendicular to the posteriorundersurface 17 enabling the chain to pass over the sprockets 26 and 35and over the arched ramp 43, but this hinging arrangement does resistpivoting of a link relative to the next as viewed on a plane parallel tothe posterior undersurface 17 which prevents twisting of the cleats(around an axis passing through the attachment link 27 and perpendicularto the posterior undersurface 17) due to asymetrical loading of thecleat.

The chain 19 is longitudinally guided by a channel 39 while passingunder the posterior ski portion 14. The channel 39 is formed in theposterior undersurface 17 for guiding the chain 19 between the sprockets29 and 35, for sheltering the chain from lateral movement between theski 11 and the snow which occurs extensively during turning and brakingmaneuvers, and for supporting the chain (slightly ahead and slightlybehind the attachment link 27 on alternating sides) when the chainresists the previously discussed tendency of the cleats to twist due toasymetrical loading and tries to cause the chain to assume a zig-zagconfiguration as viewed on a plane which is parallel to the posteriorundersurface 17.

A general view of a power driven ski 10 is shown in FIG. 7. It should benoted that in order to maximize traction capability a skier may wear apair of power driven skis, however, a combination of a power driven skion one foot and a conventional ski on the other foot provides adequatetraction for negotiating a wide range of topographical and snowconditions, and since this combination is substantially simpler in termsof hardware, it is deemed a preferred arrangement at least for leisuretype usage of the power driven ski. Further, by favoring the footwearing the power driven ski in distributing his body's weight, theskier can overcome spots where increased traction is required, such aswhen starting from stand still on a steep hill, etc. It may be furthernoted that as soon as the skier gathers speed the skis glide on the snowwith minimal resistance.

A modified embodiment of the present invention (shown in FIG. 6) wherean endless tread 118 has two tension carrying members in the form ofchains 119 which contain attachment links 127. The chains move adjacentto and obtain longitudinal guidance and sheltering from the sides of theposterior ski portion 114. The tread 118 tends to be heavier and moreexpensive to fabricate than the tread 18 of the preferred embodiment,however, it negates twisting of the cleats 120 around a vertical axiseffectively with its tension carrying capacity. Therefore, the modifiedembodiment should be given consideration for certain applications inwhich the cleats' frontal area 142 is being repeatedly subjected toasymetrical loading. It should be noted that the traction unit of themodified embodiment has a longitudinally smooth undersurface 117 (whichis an essential prerequisite of any traction unit that is to be used ina power driven ski according to the present invention).

It is obvious that modifications and substitutions can be made in thepower driven ski without departing from the spirit and the scope of myinvention.

I claim:
 1. In a power driven ski for .[.attachment to a skier's footand for.]. slidingly negotiating snow as with a conventional ski, saidpower driven ski having in combination;a. a ski with an aperturedividing it into an anterior ski portion having a longitudinally smoothanterior undersurface and a posterior ski portion, b. a bridge holdingsaid ski portions to each other, .[.c. means for attaching said ski to askier's foot,.]. .[.d..]. .Iadd.c. .Iaddend.an endless treadcirculateably supported around said posterior ski portion having atleast one tension carrying member and a plurality of cleats attached tosaid tension carrying member for thrusting against the snow. .[.e..]..Iadd.d. .Iaddend.means for circulateably supporting said tread aroundsaid posterior ski portion, and .[.f..]. .Iadd.e. .Iaddend.motor meanscoupled to said tread for circulating said tread around said posteriorski portion,the improvement wherein the posterior ski portion has alongitudinally smooth, snow contacting stationary undersurface and saidbridge holds said ski portions in position one relative to the other sothat said undersurfaces jointly form a longitudinally smooth skiingundersurface substantially throughout the length of said ski.
 2. A powerdriven ski as in claim 1 including a one way clutch coupling said motormeans to said tread.
 3. A power driven ski as in claim 1 wherein theengagement of one of said blades with snow near the front of saidposterior undersurface is sequenced out of phase with the disengagementof another one of said blades from snow near the rear of said posteriorundersurface.
 4. A power driven ski as in claim 1 wherein said treadblades are outwardly protruding, and the tread circulates from above tobelow said posterior ski portion through said aperture, over a frontsprocket having a first pitch-line radius and therafter over an archedramp having a substantially larger pitch-line radius, said arched rampbeing adapted to guide said cleats downwardly on an arc into gradualengagement with snow.
 5. A power driven ski as in claim 1 wherein saidposterior undersurface is stepped downwards relative to said anteriorundersurface.
 6. A power driven ski as in claim 1 wherein said bladesare outwardly protruding and are adapted to erect into the snow on abearing formed at their rear tip while engaging the snow and therebycause said tension carrying member to assume a zig-zag configuration asviewed on a plane which is parallel to the chain and perpendicular tosaid posterior undersurface, said zig-zag configuration causing tensionforces carried by said tension carrying member to negate bending momentsimposed on it by said blades which are attached to it.
 7. A power drivenski as in claim 6 wherein said tension carrying member is circulateblysupported on a drive sprocket which is coupled to said motor means, andon a rear sprocket which is mounted on said posterior ski portion byresilient means which permit said tension carrying member to assume saidzig-zag configuration without becoming stretched.
 8. A power driven skias in claim 6 wherein said tension carrying member comprises a chain oflinks hinged one to the next to permit said links to pivot one relativeto the next as viewed on a plane which is parallel to said chain and isperpendicular to said posterior undersurface, but resist such pivotingas viewed on a plane which is parallel to said posterior undersurface.9. A power driven ski as in claim 8 wherein the part of said tensioncarrying member which is under said ski is longitudinally guided in achannel in said posterior undersurface to thereby shelter said tensioncarrying member from lateral movement between the ski and snow as wellas for supporting the tread in its resistance to assume a zig-zagconfiguration on a plane that is parallel to said posterior undersurfacedue to asymetrical loading of the blades.